The invention relates to a linear guide device used as a linear guide in a machine tool, an industrial machine and the like.
Conventionally, as a linear guide for use in a machine tool, an industrial machine and the like, there is known a linear guide device, that is, a linear guide bearing device 51 shown in FIG. 8. The linear guide bearing device 51 shown in FIG. 8 comprise a guide rail 53 extending in one direction and serving as a guide member, and a slider 54 disposed in such a manner that it is freely movable along the longitudinal direction of the guide rail 53.
The guide rail 53 includes a plurality of rolling element rolling grooves 55 on the outer surface thereof in such a manner that they respectively extend in the longitudinal direction of the guide rail 53. And, the slider 54 includes a slider main body 56 so formed as to have a U-shaped section, and two end caps 57 respectively mounted on the two end faces of the slider main body 56; and, the slider 54 is disposed in such a manner that it strides the guide rail 53.
The slider 54 includes a plurality of load rolling element rolling grooves 58 which respectively correspond to their associated rolling element rolling grooves 55 of the guide rail 53. The rolling element rolling grooves 55 and the load rolling element rolling grooves 58 are respectively opposed to and combined with each other to thereby form their associated load rolling passages 61.
The slider 54 further includes a plurality of rolling element return passages 59 which are respectively formed in the interior portion of the slider 54 and extend substantially parallel to their associated load rolling element rolling grooves 58, and a plurality of curved passages 65 respectively connecting together the mutually associated load rolling passages 61 and rolling element return passages 59.
The above-mentioned load rolling passages 61, rolling element return passages 59 and curved passages 65 cooperate together in forming their associated rolling element circulation passages 66. Within each of the rolling element circulation passages 66, there are loaded a plurality of balls 60 serving as the rolling elements. The balls 60 are arranged in such a manner that they roll with a load within the load rolling passage 61 as well as they roll with no load within the curved passage 65 and rolling element return passage 59. Such rolling motion of the balls 60 allows the slider 54 to be freely movable along the longitudinal direction of the guide rail 53.
Also, over each set of the load rolling passage 61 and curved passage 65 of the slider 54, there is disposed a crowning 70 serving as an expansion portion which is formed in direction where the load rolling element rolling groove 58 moves away from its associated rolling element rolling groove 55. The reason why the crowning 70 is disposed is that it allows the balls 60 to circulate smoothly even if the balls 60 move into a load area such as the load rolling passage 61 from a no-load area such as the rolling element return passage 59, curved passage 65 and the like.
Further, the slider 54 includes, in the inside portions of the end caps 57 that are disposed opposed to the guide rail 53, tongue portions 67 each serving as a scooping portion (in other words, a take-up portion) which can be contacted with the balls 60 moving into the curved passage 65 from the load rolling passage 61 to thereby guide the balls 60 into the curved passage 65.
In the above-mentioned conventional linear guide bearing device 51, as shown in FIG. 8, in each crowning 70, in some cases, between the tongue portion 67 formed in the curved passage 65 and a ball 60a serving as a load rolling element which belongs to the balls 60 rolling with a load within the load rolling passage 61 and is situated in the end portion of the load rolling passage 51, there can exist an even number of balls 60b serving as no-load rolling elements which roll with no load. By the way, in FIG. 8, the balls 60b are present two in number.
At the then time, one of the two balls 60b serving as a no-load rolling element, which is situated on the right in FIG. 8 and is contacted with the tongue portion 67, rolls along a direction of an arrow line M2 shown in FIG. 8 which is the opposite direction to the rotation direction thereof in which the ball 60b runs up onto the tongue portion 67 and moves into the curved passage 65.
Due to this, the dynamical friction force of the linear guide bearing device 51 varies as in portions which are respectively enclosed by two-dot chained lines Qs shown in FIG. 9 and, actually, as the present dynamical friction force varies, the dynamical friction force of the ball 60b also increases, which raises an unfavorable problem.
By the way, in FIG. 9, the dynamical friction force of the linear guide bearing device 51, which is obtained when the linear guide bearing device 51 is moved in one direction extending along an arrow line S1 shown in FIG. 8, is shown as a positive dynamical friction force; and, on the other hand, the dynamical friction force, which is obtained when the linear guide bearing device 51 is moved in the other direction extending along an arrow line T1 shown in FIG. 8 which is the opposite direction to the arrow line S1 direction, is shown as a negative dynamical friction force.
The present invention aims at eliminating the drawbacks found in the above-mentioned conventional linear guide bearing device. Accordingly, it is an object of the invention to provide a linear guide device which not only can reduce a dynamical friction force generated when moving a guide member but also can control variations in the dynamical friction force.
In solving the above problems and attaining the above object, according to the invention, there is provided a linear guide device comprising: a guide member including a plurality of rolling element rolling grooves respectively formed in the outer surface thereof; a slider disposed on the guide member in such a manner that it is free to move along the guide member, the slider including a plurality of load rolling element rolling grooves respectively opposed to and combined with the rolling element rolling grooves of the guide member and cooperating with the rolling element rolling grooves in forming their associated load rolling passages, and a plurality of curved passages respectively connected to the thus formed load rolling passages; and, a plurality of rolling elements loaded in each of the load rolling passages and curved passages, the rolling elements not only rolling with a load within their associated load rolling passages but also rolling with no load within their associated curved passages, wherein, in an area ranging over each set of the load rolling passage and curved passage, there is formed an expansion portion extending in a direction where the load rolling element rolling groove moves away from its associated rolling element rolling groove, the expansion portion being structured such that, between the load rolling element that belongs to the load rolling elements rolling with a load within the load rolling passages and is situated in the end portion of the load rolling passage and a rolling element take-up portion formed in each of the curved passages, there can be present an odd number of no-load rolling element (elements) rolling with no load.
In other words, according to the present linear guide device, there is formed the expansion portion in such a manner that, between each curved passage and the load rolling element that belongs to the load rolling elements rolling with a load within their associated load rolling passage and is situated in the end portion of the present load rolling passage, there can be present an odd number of no-load rolling element (elements).
The no-load rolling element, which is going to move into the curved passage from the load rolling passage, is made to roll in a direction in which it can move easily into the curved passage, thereby being able not only to reduce the dynamical friction force a of the no-load rolling element generated when it moves along the guide member but also to control variations in the present dynamical friction force.
The present disclosure relates to subject matter contained in Japanese Patent Application No. Hei. 10-289379, filed on Oct. 12, 1998, and which is expressly incorporated herein by reference in its entirety.